Radar systems and method for backing a trailer

ABSTRACT

A RADAR system and associated methods are used to detect obstacles obscured from view when backing a trailer. An autonomous tractor is equipped with a rear facing RADAR device that has a field-of-view under the trailer and is configured to output RADAR returns from reflections. A controller of the tractor classifies RADAR returns from the RADAR device according to a number of reflections by a dock wall and a trailer face (e.g., a back end of the trailer) of a corresponding RADAR beam. The RADAR returns are correlated based on distance, and distance of a RADAR return from an obstacle is corrected based on the number of reflections. Advantageously, by processing RADAR returns from both direct and reflected RADAR beams, the controller is able to detect obstacles hidden behind the trailer and flag the obstacles as a hazard.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application benefits from and claims priority to U.S. ProvisionalPatent Application Ser. No. 63/289,610, filed Dec. 14, 2021. The entiredisclosure of the aforementioned application is incorporated byreference herein as if fully set forth.

BACKGROUND

Trucks are an essential part of modern commerce. These trucks transportmaterials and finished goods across the continent within their largeinterior spaces. Such goods are loaded and unloaded at variousfacilities that can include manufacturers, ports, distributors,retailers, and end users. The start and end locations are referred to as“yards” and include areas that trailers are parked (and/or staged) andmoved to and from for access by tractors (trucks) for loading to a dockdoor for loading/unloading cargo into the associated facility, leavingthe yard for travel to its destination, or entering the yard from itsdestination. Autonomous yard vehicle technology includes tractors(trucks) that are capable of automatically (without human intervention,or with human intervention via teleoperation) coupling, decoupling, andmaneuvering trailers that are within the yard.

Safety is of upmost importance in such automated yards. The automaticmaneuvering of said trailers results in situations where, if a person orother obstacle is in the intended path of the trailer or tractor,because there is no human operating the tractor, there are situationswhere the tractor may not know of a human or obstacle. Thus, additionalsensors are desired so that the controller of the automated tractor canmaneuver the trailers safely.

Additional difficulties arise because various manufacturers and freightcompanies have their own trailers. Thus, while an automated yard vehiclemay have associated sensors, it is difficult to utilize sensors on thetrailers themselves because it requires human (or machine) interventionon the trailer prior to maneuvering the trailer. This additionalintervention step is timely and creates an additional location forsafety concern.

SUMMARY

The present embodiments acknowledge the above-discussed disadvantagesthat an autonomous yard vehicle (tractor or truck) needs sufficient datato safely and efficiently operate maneuvers of a trailer around anautomated yard. The present embodiments resolve the above-discusseddisadvantages by providing a rear-facing radio detection and ranging(RADAR) system that is mounted on the autonomous yard vehicle andadapted with a field of view that scans under the coupled trailer,receives reflections of such scans, and uses techniques such as time offlight and phased array transmitter/receiver antennae to identifyvarious reflections as obstacles, the trailer itself, or yard referencestructures (such as walls, dock walls, yard structures/buildings, posts,etc.). The identified reflections are correlated to potential safetyhazards and used by the automated yard vehicle's control system tomaneuver the trailer to a desired position (e.g., by calculating thetrailer angle via said reflections). Advantageously, the presentembodiments purposefully desire to receive numerous multi-pathreflections from the RADAR scan (whereas typical RADARs include variousfilters to remove multi-path RADAR signal reflections as noise). Thenumerous reflections allow the present embodiments to see around variousobstacles associated with the trailer (e.g., the trailer wheels, etc.)where an obstacle may otherwise be hidden from view by the RADAR system.

In one embodiment, a system for backing a trailer includes: a RADARdevice adapted to mount on a tractor with a field-of-view (FOV) rearwardof the tractor such that, when the tractor is coupled to the trailer,the FOV is under the trailer, and a controller coupled to the radardevice and operable to: control the RADAR device to transmit a pluralityof transmitted signals within the FOV, receive, from the RADAR device,at least one return signal being at least one reflection of at least oneof the plurality of transmitted signals and corresponding to an obstaclebehind the trailer, the return signal defining a perceived location ofthe obstacle, and determine a correct location of the obstacle based onthe perceived location and a number of reflections made by the returnsignal.

In another embodiment, a method for backing a trailer includes:estimating a dock wall and a trailer face, classifying RADAR returnsignals according to a number of reflections of a corresponding RADARtransmitted signal, updating classifications according to velocityproperty of the RADAR return signals, correcting position of the RADARreturn signals according to the classification, and flagging obstaclespositioned behind the trailer based upon the corrected position of theRADAR return signals.

In another embodiment, a method for maneuvering a trailer includes:transmitting a radio detection and ranging (RADAR) transmitted signalbeneath the trailer; receiving return RADAR signals based on thetransmitted signal; processing the return RADAR signals to identify atleast one obstacle behind the trailer; and initiating a maneuver of thetrailer when the return RADAR signals indicate an obstacle is locatedbehind the trailer.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an aerial view showing one example autonomous yard that usesan autonomous tractor to move trailers between a staging area andloading docks of a warehouse, in embodiments.

FIG. 2 is a block diagram illustrating key functional components of theautonomous tractor of FIG. 1 , in embodiments.

FIG. 3 shows the maneuvering module of the controller of FIG. 2 infurther example detail, in embodiments.

FIG. 4 is a schematic plan view illustrating one example mission for thetractor to deposit the trailer in a drop-off spot within unloading areaof the autonomous yard of FIG. 1 , in embodiments.

FIGS. 5A and 5B are flowcharts illustrating one example method forbacking the trailer into the drop-off spot of FIG. 4 , in embodiments.

FIG. 6 is a schematic showing a restricted view from an autonomoustractor when reversing a trailer up to a loading dock, in embodiments.

FIG. 7A is a side-view schematic showing example propagation of radiowaves from the rear facing RADAR device of the tractor beneath thetrailer, in embodiments.

FIG. 7B is a plan-view schematic showing the example propagation ofradio waves from the rear facing RADAR device of the tractor beneath thetrailer of FIG. 7A, in embodiments.

FIG. 8 shows a 2D representation of example RADAR returns detected bythe RADAR device of FIG. 2 , in embodiments.

FIG. 9 is a block diagram illustrating the perception module of FIG. 2in further example detail, in embodiments.

FIG. 10 is a flowchart illustrating one example RADAR method for backinga trailer, in embodiments.

FIG. 11A shows one example 2D representation of example RADAR returnsdetected by the RADAR device of FIG. 2 when no obstacle is behind thetrailer, in embodiments.

FIG. 11B shows one example 2D representation of example RADAR returnsdetected by the RADAR device of FIG. 2 when an obstacle is locationbehind the trailer, in embodiments.

FIG. 12 is a flowchart illustrating one example method for maneuvering atrailer, in embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In an automated yard, an autonomous tractor moves trailers betweenstaging areas and loading docks for unloading and/or loading. Theautonomous tractor repeatedly couples (hitches) to a trailer, moves thetrailer, and then decouples (unhitches) from the trailer. Duringmaneuvering of the trailer, particularly when backing, there exists aneed to be able to “see” behind the trailer to prevent safety hazardissues when persons or obstacles are behind the trailer. Sensors locatedon the trailer, as opposed to the tractor, are inefficient andineffective because they require intervention with the trailer prior toautonomous maneuvering. Visual (camera-based) sensors located on theautonomous yard vehicle are ineffective and inefficient because thefield of view is blocked from the trailer itself. Moreover, attempts tovisually view under the trailer are still blocked by the trailer wheelsand other underneath components. Utilizing external sensors (such ascameras, motion sensors, and other sensor systems) external to thetrailer (e.g., mounted on the wall, or via a drone) are also inefficientand ineffective because they require additional hardware mountedthroughout the yard. Moreover, weather may prevent one or more of theseexternal systems from operation.

FIG. 1 is an aerial view showing one example autonomous yard 100 (e.g.,a goods handling facility, shipping facility, etc.) that uses anautonomous tractor 104 to move trailers 106 between a staging area 130and loading docks of a warehouse 110. The autonomous tractor 104 may bean electric vehicle or may use a combustion-based engine such as adiesel tractor. For example, an over-the-road (OTR) tractors 108 delivergoods-laden trailers 106 from remote locations and retrieve trailers 106for return to such locations (or elsewhere-such as a storage depot). Ina standard operational procedure, OTR tractor 108 arrives with trailer106 and checks-in at a facility entrance checkpoint 109. Aguard/attendant enters information (e.g., trailer number or QR (ID) codescan-embedded information already in the system, which would typicallyinclude: trailer make/model/year/service connection location, etc.) intoa mission controller 102 (e.g., a computer software server that may belocated offsite, in the cloud, fully onsite, or partially located withina facility building complex, shown as a warehouse 110). Warehouse 110includes perimeter loading docks (located on one or more sides of thebuilding), associated (typically elevated) cargo portals and doors, andfloor storage, all arranged in a manner familiar to those of skill inshipping, logistics, and the like.

By way of a simplified operational example, after arrival of OTR tractor108 and trailer 106, the guard/attendant at checkpoint 109 directs thedriver to deliver trailer 106 to a specific numbered parking space in adesignated staging area 130, which may include a large array ofside-by-side trailer parking locations, arranged as appropriate for thefacility's overall layout.

Once the driver has parked the trailer in the designated parking spaceof the staging area 130, he/she disconnects the service lines andensures that connectors are in an accessible position (i.e. ifadjustable/sealable), and decouples OTR tractor 108 from trailer 106. Iftrailer 106 is equipped with swing doors, this can also provide anopportunity for the driver to unlatch and clip trailer doors in the openposition, if directed by yard personnel to do so.

At some later time, (e.g., when warehouse is ready to process the loadedtrailer) mission controller 102 directs (e.g., commands or otherwisecontrols) tractor 104 to automatically couple (e.g., hitch and, in someembodiments couple to air and/or electrical lines) with trailer 106 at apick-up spot in staging area 130 and move trailer 106 to a drop-off spotat an assigned unloading dock in unloading area 140 for example.Accordingly, tractor 104 couples with trailer 106 at the pick-up spot,moves trailer 106 to unloading area 140, and then backs trailer 106 intothe assigned loading dock at the drop-off spot such that the rear oftrailer 106 is positioned in close proximity with the portal and cargodoors of warehouse 110. The pick-up spot and drop-off spot may be anydesignated trailer parking location in staging area 130, any loadingdock in unloading area 140, and any loading dock within loading area150.

Manual and/or automated techniques are used to offload the cargo fromtrailer 106 and into warehouse 110. During unloading, tractor 104 mayremain hitched to trailer 106 or may decouple (e.g., unhitch) to performother tasks. After unloading, mission controller 102 directs tractor 104to move trailer 106 from a pick-up spot in unloading area 140 and to adrop-off spot, either returning trailer 106 to staging area 130 ordelivering trailer 106 to an assigned loading dock in a loading area 150of warehouse 110, where trailer 106 is then loaded. Once loaded, missioncontroller 102 directs tractor 104 to move trailer 106 from a pick-upspot in loading area 150 to a drop-off spot in staging area 130 where itmay await collection by another (or the same) OTR tractor 108. Given thepick-up spot and the drop-off spot, tractor 104 may autonomously movetrailer 106.

FIG. 2 is a block diagram illustrating key functional components oftractor 104. Tractor 104 includes a battery 202 for powering componentsof tractor 104 and a controller 206 with at least one digital processor208 communicatively coupled with memory 210 that may include one or bothof volatile memory (e.g., RAM, SRAM, etc.) and non-volatile memory(e.g., PROM, FLASH, Magnetic, Optical, etc.). Memory 210 stores aplurality of software modules including machine-readable instructionsthat, when executed by the at least one processor 208, cause the atleast one processor 208 to implement functionality of tractor 104 asdescribed herein to operate autonomously within autonomous yard 100under direction from mission controller 102.

Tractor 104 also includes at least one drive motor 212 controlled by adrive circuit 214 to mechanically drive a plurality of wheels (notshown) to maneuver tractor 104. Drive circuit 214 includes a safetyfeature 215 that deactivates motion of tractor 104 when it detects thatrotation of drive motor 212 is impeded (e.g., stalled) and that drivemotor 212 is drawing a current at or greater than a stalled threshold(e.g., above one of 400A, 500A, 600A, 700A, etc. depending on theconfiguration of the drive motor 212), for a predetermined period (e.g.,five seconds). Safety feature 215 may thereby prevent damage to tractor104 and/or other objects around tractor 104 when tractor 104 is impededby an object. Safety feature 215 is described above with respect to anelectric tractor. It should be appreciated that a similar safety featurecould be included for diesel-based or other types of tractors, such asreducing engine power when an RPM threshold goes above a pre-setthreshold. When safety feature 215 is tripped, tractor 104 requiresmanual reactivation before being able to resume movement. Accordingly,tripping safety feature 215 is undesirable.

Tractor 104 also includes a location unit 216 (e.g., a GPS receiver)that determines an absolute location and orientation of tractor 104, aplurality of cameras 218 for capturing images of objects around tractor104, and at least one Light Detection and Ranging (LIDAR) device 220(hereinafter LIDAR 220) for determining a point cloud about tractor 104.Location unit 216, the plurality of cameras 218, and the at least oneLIDAR 220 cooperate with controller 206 to enable autonomousmaneuverability and safety of tractor 104. Tractor 104 includes a fifthwheel (FW) 222 for coupling with trailer 106 and a FW actuator 224controlled by controller 206 to position FW 222 at a desired height. Incertain embodiments, FW actuator 224 includes an electric motor coupledwith a hydraulic pump that drives a hydraulic piston that moves FW 222.However, FW actuator 224 may include other devices for positioning FW222 without departing from the scope hereof. Tractor 104 may alsoinclude an air actuator 238 that controls air supplied to trailer 106and a brake actuator 239 that controls brakes of tractor 104 and trailer106 when connected thereto via air actuator 238.

Controller 206 also includes a trailer angle module 232 that determinesa trailer angle 233 between tractor 104 and trailer 106 based on one orboth of a trailer angle measured by an optical encoder 204 positionednear FW 222 and mechanically coupled with trailer 106 and a point cloud221 captured by the at least one LIDAR 220.

Tractor 104 also includes an alignment module 260 that provides improvedlocalized alignment of tractor 104 such as when at a loading/unloadingdock in unloading area 140 and loading area 150.

Controller 206 may implement a function state machine 226 that controlsoperation of tractor 104 based upon commands (requests) received frommission controller 102. For example, mission controller 102 may receivea request (e.g., via an API, and/or via a GUI used by a dispatchoperator, or via a mission planning algorithm that manages actions to betaken by the tractor) to move trailer 106 from a first location (e.g.,slot X in staging area 130) to a second location (e.g., loading dock Yin unloading area 140). Once this request is validated, missioncontroller 102 invokes a mission planner 103 (e.g., a software package)that computes a ‘mission plan’ (e.g., see mission plan 320, FIG. 3 ) foreach tractor 104. For example, the mission plan is an ordered sequenceof high level primitives to be followed by tractor 104, in order to movetrailer 106 from location X to location Y. The mission plan may includeprimitives such as drive along a first route, couple with trailer 106 inparking location X, drive along a second route, back trailer 106 into aloading dock, and decouple from trailer 106.

Function state machine 226 includes a plurality of states, eachassociated with at least one software routine (e.g., machine-readableinstructions) that is executed by processor 208 to implements aparticular function of tractor 104. Function state machine 226 maytransition through one or more states when following the primitives frommission controller 102 to complete the mission plan.

Controller 206 may also include an articulated maneuvering module 240,implemented as machine-readable instructions that, when executed byprocessor 208, cause processor 208 to control drive circuit 214 andsteering actuator 225 to maneuver tractor 104 based on directives frommission controller 102.

Controller 206 may also include a navigation module 234 that useslocation unit 216 to determine a current location and orientation oftractor 104. Navigation module 234 may also use other sensors (e.g.,camera 218 and/or LIDAR 220) to determine the current location andorientation of tractor 104 using dead-reckoning techniques.

Tractor 104 may also include a rear facing radio detection and ranging(RADAR) device 270 and controller 206 may include a perception module280, implemented as machine readable instructions stored in memory 210and executable by processor 208, that processes returns from RADARdevice 270 to detect and identify obstacles 281 behind trailer 106,particularly when tractor 104 is reversing trailer 106 into a parkingspot and/or loading dock. Operation of RADAR device 270 and perceptionmodule 280 is described in further detail below.

Articulated Backing

FIG. 3 shows maneuvering module 240 of controller 206, FIG. 2 , infurther example detail. Maneuvering module 240 includes a missionexecutor 304 and a motion planner 306. Mission executor 304 may receive,from mission planner 103 running in mission controller 102, a missionplan 320 that defines an ordered list of mission segments, where eachmission segment is a high-level primitive defining at least one activityto be performed by tractor 104. Mission executor 304 executes missionplan 320 by coordinating operation of one or more components of tractor104. For example, mission executor 304 may define at least one path 322that motion planner 306 controls tractor 104 to follow. For example,motion planner 306 may control steering angle 250 and throttle value 252and use one or more inputs including trailer angle 233, and navigationdata (e.g., a current location and orientation) from navigation module234, and so on, to control tractor 104 to follow path 322. Accordingly,motion planner 306 causes tractor 104 to execute maneuvers andaccomplish mission goals defined by mission plan 320. Examples ofmission goals include achieving a given pose (e.g., location andorientation), follow a waypoint plan, and so on. These mission goals maybe defined by mission plan 320 or may be generated, based on missionplan 320, by mission executor 304.

FIG. 4 is a schematic plan view illustrating one example mission fortractor 104 to deposit trailer 106 in a drop-off spot 470 (e.g., aloading dock 432) within unloading area 140 of autonomous yard 100 ofFIG. 1 . Tractor 104 positions trailer 106 in preparation for backingtrailer 106 into a drop-off spot 470, which in this example is one of aplurality of loading docks 432 of unloading area 140 of warehouse 110.Each loading dock 432 has a loading door 434, with which the parkedtrailers align. In the Example of FIG. 4 , no trailer is parked atdrop-off spot 470, which corresponds to loading dock 432(3); however,loading docks 432(2) and 432(4), which are adjacent to loading dock432(3), each have a parked trailer. Since trailer doors are at the rearof trailer 106, trailer 106 is reversed up to loading dock 432 and iscorrectly aligned with loading door 434 to provide full and safe accessto trailer 106. A reference path 476, centered on drop-off spot 470(e.g., loading dock 432(3)) may be determined by controller 206 tofacilitate alignment of trailer 106 when backing into drop-off spot 470.Controller 206 may determine a staging path 474 for tractor 104 tofollow to approach drop-off spot 470. Staging path 474 is determinedbased upon a starting orientation and location of tractor 104 andtrailer 106 relative to drop-off spot 470 and is selected to positionboth tractor 104 and trailer 106 at the desired staging point 472, withthe desired orientation, and with and angle of trailer 106 relative totractor 104, substantially zero. As tractor 104, shown as outline 478,passes drop-off spot 470 while proceeding to staging point 472, tractor104 may scan (e.g., using cameras 218 and/or LIDAR 220, drop-off spot470 to determine that obstacles are not blocking maneuvering of trailer106 into drop-off spot 470.

Trailer Backing Method

FIGS. 5A and 5B are flowcharts illustrating one example method 500 forbacking trailer 106. For example, method 500 may be used to back trailer106 into drop-off spot 470 of FIG. 4 . The following example continuesthe mission, received from mission controller 102, to move trailer 106from a pick-up spot (not shown) to drop-off spot 470. Method 500 is, forexample, implemented at least in part by controller 206 of tractor 104that executes computer readable instructions to cause tractor 104 toautonomously back trailer 106 into drop-off spot 470. In block 502,method 500 performs precondition checks. In one example of block 502,controller 206 checks that trailer 106 is attached to tractor 104 byverifying that FW 222 is locked and kingpin 308 is sensed within FW 222.In block 504, method 500 received drop-off spot information and computesmaximum apron clearance. In one example of block 504, controller 206uses location information of drop-off spot 470, received from missioncontroller 102, to compute freespace 480 near drop-off spot 470 byprojecting lines radially from a front location of drop-off spot 470 tointersect with a line of any polygon defining structure (e.g., anothertrailer parking spot, a no-go area, an area boundary, a building, awall, etc.) of autonomous yard 100.

Block 506 is only executed when drop-off spot 470 is a loading dock. Inblock 506, method 500 begins checking the loading dock status signal. Inone example of block 506, controller 206 receives the loading dockstatus signal indicative of loading dock 432(3) at drop-off spot 470being ready to receive trailer 106.

In block 508, method 500 begins obstacle checks against a polygon ofdrop-off spot with backoff. Any object detected within drop-off spot 470may prevent trailer 106 from entering or being parked at drop-off spot470. In one example of block 508, controller 206 uses LIDAR 220 tocapture point cloud 221 of drop-off spot 470 and processes point cloud221 to detect objects within drop-off spot 470, allowing for backoff ofa small distance that ensures that trailer bumpers at a loading dock anda parking curb within staging area 130 are not detected as objectspreventing parking of trailer 106. In certain embodiments, controller206 may also use other sensors (e.g., cameras, SONAR, and/or RADAR) tocapture data of drop-off spot 470 that may also, or alternatively, beused to detect objects within drop-off spot 470 that may prevent parkingof trailer 106 therein.

Block 510 is a decision. If, in block 510, method 500 determines that anobstacle is present, method continues with block 512; otherwise, method500 continues with block 514. In block 512, method 500 gets help from aremote operator or remote device.

In block 514, method 500 drives the tractor and the trailer forwardsalong a staging path. In one example of block 514, controller 206controls tractor 104 to pull trailer 106 along staging path 474 thatpositions tractor 104 and trailer 106 for reversing into drop-off spot470. Block 516 is a decision. If, in block 516, method 500 determinesthat the trailer angle is not within a predefines tolerance of zero,method 500 continues with block 518; otherwise, method 500 continueswith block 520. In one example of block 516, while tractor 104 isstopped at staging point 472, controller 206 determines, based ontrailer angle 233 being approximately zero, whether trailer 106 isaligned with tractor 104. In block 518, when the trailer angle is notclose enough to zero and to correct the trailer angle, method 500 moves(e.g., called a “push-out” maneuver) tractor 104 forward in a straightline for a predefined distance, and then reverses tractor 104 andtrailer 106 straight backwards to staging point 472. Staging path 474 isdesigned with a built-in push-out, but in certain circumstances, thebuilt-in push-out is insufficient to straighten trailer 106. Whenbacking trailer 106, it is advantageous to start the backing with asubstantially zero trailer angle.

In block 520, method 500 begins the reversing maneuver to back thetrailer into the drop-off spot. In one example of block 520, controller206 controls tractor 104 to back trailer 106 along backing path 482 intodrop-off spot 470. For example, controller 206 may control steeringactuator 225 of tractor 104 to maneuver tractor 104 into freespace 480as needed to reverse the back end of trailer 106 along backing path 482and into drop-off spot 470 without trailer 106 or tractor 104encroaching on other parking spaces or structures of autonomous yard100. In block 522, method 500 invokes a retry if necessary. In oneexample of block 522, controller 206 detects that the current locationof trailer 106 relative to backing path 482 exceeds a predefinedtolerance and invokes a retry of the backing maneuver, wherebycontroller 206 controls tractor 104 to pull forward, along referencepath 476 for example, to align with drop-off spot 470, and then reversestrailer 106 into drop-off spot 470, along reference path 476 forexample.

Block 524 is a decision. If, in block 524, method 500 determines thatthe drop-off spot is a parking spot, method 500 continues with block526; otherwise, method 500 continues with block 528. In block 526,method 500 backs to position the trailer front end at a front of theparking spot. In one example of block 526, controller 206 positions afront end of trailer 106 at a front of drop-off spot 470. For example,this positions the front of each trailer at the front of the parkingspot irrespective of trailer length. Geometry of each parking spot isdefined when autonomous yard 100 is commissioned, whereby each parkingspot may be sized to accommodate all trailer lengths used withinautonomous yard 100. Method 500 continues with block 532.

In block 528, method 500 backs to position the trailer back at the backof the drop-off spot. In one example of block 528, controller 206 backstrailer 106 into drop-off spot 470 such that the back end of trailer 106is at the back end of drop-off spot 470. Since drop-off spot 470 is aloading dock (e.g., loading dock 432(3)), it is important that the backend of trailer 106 be immediately in front of loading door 434(3). Inblock 530, method 500 invokes a dock tractor function. In one example ofblock 530, controller 206 invokes a dock function that uses drivecircuit 214 to applies throttle to push trailer 106 against bumpers ofloading dock 432(3) to minimize rebound, and brakes of trailer areapplied such that trailer 106 remains positioned directly in front ofloading dock 432(3).

In block 532, method 500 evaluates whether the trailer is positionedwithin the drop-off spot acceptably. In one example of block 532,controller 206 uses one or more of location unit 216, trailer angle 233,known dimensions of trailer 106, camera 218, and LIDAR 220 to evaluatethe position of trailer 106 within drop-off spot 470. Where drop-offspot 470 is a parking spot, controller 206 determines that trailer 106is contained within the polygon defined for the parking spot. Wheredrop-off spot 470 is a loading dock, controller 206 evaluates whether anestimated position of the back end of trailer 106 is within a desiredlateral accuracy of a center (e.g., a reference path 476) of loadingdock 432(3).

Block 534 is a decision. If, in block 534, method 500 determines thatthe position of trailer is acceptable, method 500 terminates; otherwise,method 500 continues with block 536. In block 536, method 500 invokes aretry. In one example of block 536, controller 206 controls tractor 104to pull trailer 106 straight ahead (e.g., along reference path 476) fora distance determined by freespace 480 (e.g., from apron clearance). Atthe end of this path, controller 206 control tractor 104 to back trailer106 along reference path 476 into drop-off spot 470, repeating blocks520 through 534 up to a maximum number of retries.

FIG. 6 is a schematic showing a restricted view from autonomous tractor104 when reversing trailer 106 up to loading dock 432. In this example,tractor 104 uses multiple rear facing cameras 218 and/or LIDAR 220 toassist with maneuvering, however, trailer 106 obscures any view tractor104 has of an area immediately behind trailer 106. Although, asdescribed above, many different safety procedures (e.g., drive by) maybe implemented, when reversing, any object that moves into the areabehind trailer 106 is not detected by tractor 104.

As shown in FIG. 6 , tractor 104 has two rear-facing cameras 218(1)-(2),one positioned at each side of tractor 104, near wing mirrors forexample, such that each has a rearward field of view 602 that includes acorresponding side of trailer 106. As tractor 104 is reversing trailer106 into loading dock 432(3), controller 206 evaluates images capturedby cameras 218, identifies any markings (e.g., fiducial markings, nativeobjects) captured in the images, and computes a relative navigationsolution for tractor 104 relative to the identified markings and theirposition within the images. Alignment module 260 uses the images andmarking to improve location and orientation of tractor 104 relative toloading dock 432(3), as compared to location and orientation determinedby location unit 216 from an inertial navigation system and/or odometrywhere drift errors may occur, and from availability of GPS signals wherediscontinuities and canyon effect errors may occur.

In certain embodiments, another camera 218(3) may be fitted to anextendable mast 620 coupled with tractor 104. As trailer 106 approachesloading dock 432, mast 620 may be extended to provide camera 218(3) witha higher vantage point that provides camera 218(3) with a view overtrailer 106. However, even with mast 620, trailer 106 blocks a view ofan area immediately behind trailer 106.

Conventionally, the location of the back end of trailer 106 is estimatedbased on trailer angle 233 and a current location and orientation oftractor 104. Advantageously, by determining the location of the back endof trailer 106 relative to loading dock 432, tractor 104 may moreaccurately position trailer 106 at loading dock 432.

FIG. 7A is a side-view schematic showing example propagation of radiowaves (RADAR beams, also referred to as RADAR signals) from the rearfacing RADAR device 270 of tractor 104 beneath trailer 106. FIG. 7B is aplan-view schematic showing the example propagation of radio waves fromthe rear facing RADAR device 270 of tractor 104 beneath trailer 106 ofFIG. 7A. FIGS. 7A and 7B are best viewed together with the followingdescription. RADAR device 270 is attached to a back end of tractor 104and faces beneath trailer 106. In embodiments, RADAR device 270 is aphased array, multiple transmit, multiple receive (MIMO) RADAR device(also known as digitally modulated RADAR) having a forty-degree verticalfield of view and operating in the 77-80 Ghz band to provide4-dimensional point cloud (4th dimension representing velocity of themeasured point). RADAR device 270 may represent one of the HM11Radar-on-a-chip devices from Uhnder, Inc. and the Eagle device fromOculii. For example, RADAR device 270 may have an Azimuth resolution of0.8 degrees, an Elevation resolution of 0.8 degrees, a range resolutionof 5 cm (Occuli) or 10 cm (uhnder), and a velocity resolution of 0.27m/second.

RADAR device 270 emits multiple radio wave transmitted signals 708(e.g., a scanning RADAR beam) beneath trailer 106, and detects RADARreturn signal(s) resulting from the transmitted signals 708, orreflections thereof, reflecting off objects in the path of transmittedsignals 708. Each scan may generate a corresponding RADAR point cloud271 (see FIG. 2 ) that includes the corresponding RADAR returnsignal(s). These returns may result from structure forming the undersideof trailer 106 and other objects there beyond. As shown in FIG. 7A,underhanging objects, such as landing gear 704, rear wheels 706, andother infrastructure (bogies, mud flaps, etc.) and ground-basedstructures may reflect and thus block certain ones of transmittedsignals, however, other of transmitted signals 708 may emerge behindtrailer 106. Some transmitted signals may be unimpeded and emerge fromthe rear of trailer 106. Some transmitted signals 708 may bounce off theground and then emerge from the rear of trailer 106. For example, asshown in FIG. 7A, after bouncing off the ground, certain transmittedsignals 708 may then pass between wheels 706 and emerge behind trailer106. Other transmitted signals may bound of the underside of the trailerand emerge behind the trailer. Accordingly, some emerging transmittedsignals 708 are direct, and other emerging transmitted signals arereflected off the ground and/or the underside of trailer 106.

As noted above, conventional RADAR devices are configured to rejectand/or ignore multi-path reflections, since these multi-path reflectionsare typically unwanted noise that confuses perception of directreflections. However, the present embodiments advantageously capture anduse multi-path reflections to detect objects behind trailer 106 thatwould otherwise be undetectable. As shown in FIG. 7B, transmittedsignals 712 that pass beneath trailer 106 to reach the area behindtrailer 106 are reflected from the loading dock wall 710 back towardstrailer 106 as reflected signals 714 (a.k.a., “return signals”). Atleast some of reflected signal 714 are reflected by a back end 715 oftrailer 106, shown as double-reflected signals 716, back towards theloading dock wall 710 and so on. Advantageously, these signals 712, 714,and 716 indicate similar patterns of reflection that may be correlatedas obstacle locations. For example, certain groupings in a linearpattern parallel to the back of the trailer may be used to determine thelocation of the dock wall relative to the RADAR device 270. Accordingly,RADAR device 270 generates a list of received reflections (e.g.,range/azimuth/elevation/velocity of the returned energy) that may beused to detect obstacles hidden behind trailer 106.

It is further noted that, as shown in FIG. 7A, the vertical FOV of RADARdevice 270 is restricted by trailer 106, and that the effect of any suchvertical component on the indicated and/or corrected distance isnegligible, and therefore the vertical component of the RADAR returns isignored.

FIG. 8 shows a 2D representation 800 of example RADAR returns detectedby RADAR device 270 of FIG. 2 . 2D representation 800 indicates RADARreturns as dots having a size and/or color representing the intensity ofthe detected return, and where the position of the dot within the 2Drepresentation 800 indicates the presumed location of the objectreflecting the RADAR signal and is based on the direction and time ofthe detected RADAR return signal. In the example of FIG. 8 , theobstacle is positioned behind the wheels of trailer 106 and is notimpinged by the direct beam of transmitted signals 712; however, theobstacle is impinged by both the reflected signals 714 and 716.

In the example of FIG. 8 , 2D representation 800 shows line representinga dock wall 802 (e.g., a wall of loading dock 432). The linerepresenting a dock wall 802 may be determined from one or more othersources such as LIDAR point cloud 221, mapped structures within yard100, and/or RADAR returns defining a consistent pattern (or groupings)corresponding to a potential dock wall (e.g., the pattern is at the samelocation as the dock wall defined in LIDAR and/or mapped structures (GPSdata)). 2D representation 800 also shows a line representing a trailerface 804 (e.g., a back end of trailer 106). The lines for dock wall 802and trailer face 804 are shown for illustration purposes and may bedefined and/or stored elsewhere. 2D representation 800 also shows manyreturns 806 from beneath trailer 106.

2D representation 800 also shows a return 808 corresponding to a firstreflection of trailer 106 from dock wall 802, and a return 810corresponding to a second reflection of dock wall 802 off trailer face804 off dock wall 802. As appreciated, return 808 appears at a firstdistance beyond dock wall 802, where the first distance is equal to thedistance between trailer face 804 and dock wall 802. Similarly, return810 appears at twice the first distance beyond dock wall 802.Understanding of relationships between these reflections and returnsallows other returns to be identified, particularly where the returnsthat appear behind location of a dock wall are only there because theyare reflected return signals because the dock wall would otherwiseprevent the RADAR transmitted signals from transmitting past the dockwall with sufficient signal strength. As seen in 2D representation 800,a weak obstacle return 812 appears near return 808 and corresponds to anobstacle positioned at the edge (e.g., at an edge of a virtual FOV) ofreflected signals 714, and a strong obstacle return 814 appears nearreturn 810 and corresponds to the obstacle reflecting double-reflectedsignals 716. That is, the obstacle was positioned behind trailer 106such that no direct transmitted signals 708 impinged upon it, andtherefore there was no direct return (e.g., a single reflected returnsignal) but as the RADAR continued to bounce back-and-forth, signalsreflected off the obstacle were detectable by the device 270. Byunderstanding the multiple reflections of RADAR signals between dockwall 802 and trailer face 804 (e.g., back end 715 of trailer 106),return signals detected by RADAR device 270 may be processed to detectobstacles behind trailer 106 that are otherwise not visible to camera orLIDAR-based obstacle detection systems because they are not visible dueto the trailer, or wheels, or other obstacles blocking line-of-sitebetween the camera/LIDAR and the potential obstacle.

Discriminating one obstacle from another using radar returns is based ondetermined contrast between the returns. The contrast is acharacteristic of the detected signal and may be based upon one or bothof spatial contrast, such as range/azimuth/elevation of the returnedenergy, and contrast in some measured property, such as velocity and/orsignal intensity. Thus, the terms “weak” and “strong” as used hereinrefers to relative contrast in signal characteristic between twodetected RADAR signals.

FIG. 9 is a block diagram illustrating perception module 280 of FIG. 2in further example detail. Perception module 280 may be computerreadable instructions that, when executed by a processor, implement thefollowing functionality. Perception module 280 receives input definingdetected returns at RADAR device 270 and may receive input from LIDAR220, or other yard-mapping component. For example, processed data fromLIDAR 220 may define structures (e.g., a wall of loading dock 432)detected around tractor 104. As another example, a yard may be mappedsuch that the location of structures within the yard are known.Processed data corresponding to the mapped yard, either stored on-boardthe tractor 104 in memory or retrieved via connection with missioncontroller 102 or other yard management server, may define structures(e.g., a wall of loading dock 432) in proximity to the tractor's 104known location. An estimator 904 of perception module 280 receives RADARreturns from RADAR device 270, the mapping information on detectedstructures (e.g., from LIDAR 220, and/or an a priori map 902 definingstructure within yard 100), and thereby estimates an expected positionof dock wall 802 within the RADAR returns. That is, estimator 904 maycorrelate RADAR returns with other data defining expected structure todetermine dock wall 802.

A classifier 906 of perception module 280 receives the estimatedlocation of dock wall 802 from estimator 904 and classifies RADARreturns from RADAR device 270 based on whether they are direct returns(e.g., positioned at or before dock wall 802), a first bounce return(e.g., positioned beyond dock wall 802 but before return 808 and thusfrom reflected signals 714), a second bounce return (e.g., positionedbeyond return 808 and thus from double-reflected signals 716), etc.

In certain embodiments, classifier 906 may also use velocity property ofeach RADAR return for classification. Velocity of each return isprovided by RADAR device 270 and may be used to further distinguishand/or classify each RADAR return. The speed of tractor 104 may beprovided to perception module 280. Since trailer 106 is moving towardsloading dock 432 under control of tractor 104, relative to RADAR device270, the wall of loading dock 432 appears to be moving at the speed oftrailer 106, which appears stationary relative to RADAR device 270.Since the wall of loading dock 432 and the trailer face (e.g., the rearend of trailer 106) are near parallel, each reflection resulting fromthe RADAR transmitted signal 708 bouncing off of an obstacle multipliesthe measured velocity. The reported RADAR returns each define a directmeasurement of radial velocity, relative to RADAR device 270, of thereflecting object. Accordingly, a RADAR return based on a singlereflection of transmitted signal 712 reports a true velocity of thereflecting object relative to RADAR device 270, whereas a RADAR returnfrom a double-reflection (e.g. a reflection based on reflected signal714) reports double the true radial velocity, and a RADAR return atriple-reflection (e.g., based on signal 716) reports triple the trueradial velocity, and so on. The reflected trailer face 804 appears to bemoving at twice the speed of the dock wall 802. Advantageously,classifier 906 may use the velocity of each RADAR return to furtherclassify and/or to verify the classification of each RADAR return. Astractor 104 and trailer 106 are reversing, the velocity component ofstationary objects directly relates to the speed of tractor 104.Accordingly, RADAR returns may be classified based on indicated velocityto identify stationary structure and objects. That is, RADAR returnsthat do not have a velocity component directly related to the speed oftractor 104 cannot indicate a stationary object or structure.Accordingly, RADAR returns with a velocity component that does notrelate to the velocity of tractor 104 indicate a moving object that maybe flagged.

A corrector 908 of perception module 280 processes the classified RADARreturns output by classifier 906 to determine obstacles (e.g., objectsother than dock wall 802 and trailer face 804) that are located behindtrailer 106 (e.g., between trailer 106 and the wall of loading dock 432)by correcting the perceived obstacle distance based on whether the RADARreturn signal resulted from a reflection of the RADAR beam. The lateralcomponent of the RADAR return is not corrected or adjusted. In oneexample of operation, corrector 908 identifies returns 812 and 814 asrepresenting an obstacle positioned between trailer 106 and the wall ofloading dock 432 by correcting the indicated distance RADAR returnsignals 812 and 814 based upon a number of reflections for each RADARreturn signal. Accordingly, corrector 908 determines a correctedlocation (shown as point 816 in FIG. 8 ) of the obstacle and send thecorrected location of the obstacle to a flagger 910 of perception module280. That is, corrector 908 determines the correct location of theobstacle by correcting the distance according to the reflections of theRADAR signal. As shown in FIG. 8 , both returns 812 and 814 havereported locations that are beyond dock wall 802, which is a result ofthe RADAR signal being reflected before impinging upon the obstacle.Accordingly, corrector 908 adjusts the perceived distance to an actuallocation 816 by removing the distance added by the reflection(s).

Flagger 910 flags the detected obstacle with a corresponding correctedlocation and stores the detected obstacle 281 with correspondinglocation in memory 210. The flagged obstacle 281 may be used bymaneuvering module 240 to alter, stop, or otherwise maneuver the trailerto avoid obstacle 281. In certain embodiments, Flagger 910 may evaluateeach detected obstacle and corresponding corrected location againstplanned motion of tractor 104 and trailer 106 to determine whether theobstacles are in the path of trailer 106 and does not flag obstacleshaving corrected locations that are not in the path of trailer 106.

In certain embodiments, where trailer 106 is not being reversed up to adock wall (e.g., where there are no flat structures positioned behindtrailer 106), perception module 280 cannot detect dock wall 802 and maythereby determine that obstacles may be detected only by direct beam oftransmitted signals 712, since there is no dock wall to reflecttransmitted signal 712 to generate signals 714 and 716. Accordingly,perception module 280 may generate an alert (e.g., to an operator oftractor 104) to indicate that operation of RADAR device 270 is limitedto a narrower FOV behind trailer.

In certain embodiments, where perception module 280 fails to detectsufficient RADAR returns beyond trailer face 804 (e.g., the known end oftrailer 106), perception module 280 may determine that object detectionis not possible since substantially all of signals 708 are blocked bystructure beneath trailer 106. Such determination may prevent a sense offalse safety and/or false security. In one example, when sufficientRADAR returns beyond trailer face 804 are not detected, flagger 910 mayalert maneuvering module 240 and/or an operator.

FIG. 10 is a flowchart illustrating one example RADAR method 1000 forbacking a trailer. Method 1000 may be implemented using perceptionmodule 280 of controller 206 within tractor 104. In block 1002, method1000 estimates a dock wall and trailer face. In one example of block1002, estimator 904 correlates RADAR returns with other data, receivedfrom LIDAR 220 and a priori map 902 defining structure of yard 100, todetermine dock wall 802 and trailer face 804.

In block 1004, method 1000 classifies the radar returns according tonumber of reflections. In one example of block 1004, classifier 906receives the estimated location of dock wall 802 and trailer face 804from estimator 904 and classifies RADAR returns based on whether theyare direct returns, a first bounce return, and a second bounce return.In block 1006, method 1000 updates the classifications according to avelocity property. In one example of block 1006, classifier 906 uses thevelocity of each RADAR return to further classify, and/or to verify, theclassification of each RADAR return.

In block 1008, method 1000 corrects the position of returns according tothe classification. In one example of block 1008, corrector 908processes the classified RADAR returns output by classifier 906 toidentify objects other than dock wall 802 and trailer face 804 that arebehind trailer 106 (e.g., between trailer 106 and the wall of loadingdock 432) and to determine the actual position of the object bycorrecting the perceived location based upon whether the RADAR returnwas from a direct transmitted signal 712, a reflected signal 714, or adouble-reflected signal 716.

In block 1010, method 1000 flags obstacles based on planned motion ofthe trailer. In one example of block 1010, flagger 910 evaluates eachdetected obstacle and its corresponding corrected location againstplanned motion of tractor 104 and trailer 106 to determine whether theobstacles is in the path of trailer 106 and does not flag obstacleshaving corrected locations that are not in the path of trailer 106.Method 1000 repeats for each new set of RADAR returns captured by RADARdevice 270.

Although RADAR device 270 generates a 3D point cloud 271, perceptionmodule 280, in one embodiment, may process only certain RADAR returnsthat fall within a horizontal range corresponding to the height oftrailer 106 or below.

FIG. 11A shows one example 2D representation 1100 of example RADARreturns detected by RADAR device 270 of FIG. 2 when no obstacle isbehind trailer 106. FIG. 11B shows one example 2D representation 1150 ofexample RADAR returns detected by RADAR device 270 of FIG. 2 when anobstacle is location behind trailer 106. FIGS. 11A and 11B are shown inline drawings here having different shapes (e.g., squares, diamonds,triangles, stars for different characteristics of the radar return. Itshould be appreciated, however, that a given representation may be incolors instead of different shapes, such as the heat map of FIG. 8 , oras FIGS. 11A and B were shown in U.S. Provisional Patent ApplicationSer. No. 63/289,610, filed Dec. 14, 2021, and incorporated by referencehere.

Similar to 2D representation 800 of FIG. 8 , 2D representations 1100 and1150 both show a line representing a dock wall 1102 (e.g., a wall ofloading dock 432), a line representing a trailer face 1104 (e.g., a backend of trailer 106), and a line corresponding to a first reflection 1106of trailer face 1104 from dock wall 1102. FIG. 11B further shows adirect RADAR return 1152 (e.g., received from transmitted signals 712)corresponding to the obstacle, and a RADAR return 1154 (e.g., receivedfrom double-reflected signal 714) corresponding to a first reflection ofthe obstacle. Accordingly, flagger 910 flags the RADAR returns 1152 and1154 as an obstacle because they are located in an area in the 2Drepresentation that is behind the dock wall (and thus shouldn't bevisible to the RADAR). Flagger 910 may store the obstacle 281 in memory210 and notifies maneuvering module 240 accordingly.

FIG. 12 is a flowchart illustrating one example method 1200 formaneuvering a trailer. Method 1200 is, for example, implemented by thecomputer readable instructions that, when executed by processor 208implement the controller 206 of FIG. 2 . Method 1200 is, in at leastsome embodiments, implemented in combination with method 500, 1000 orother functionality and methods disclosed herein.

Block 1202 includes transmitting a radio detection and ranging (RADAR)transmitted signal beneath a trailer. In one example of block 1202,perception module 280 of controller 206 controls RADAR device 270 togenerate at least one transmitted signal (e.g., transmitted signal 712of FIGS. 7A, B).

Block 1204 includes receiving return RADAR signals based on thetransmitted signal. In one example of block 1202, perception module 280of controls RADAR device 270 to receive reflected signals based on thetransmitted signal reflecting off of one or more objects at or behindthe trailer.

Block 1206 includes processing the received return RADAR signals toidentify at least one obstacle behind the trailer. In one example ofblock 1206, perception module 280 detects obstacles 281 using thereceived reflected signals. In an embodiment, the processing thereceived return RADAR signals including identifying a number ofreflections of one or more of the received return RADAR signals, and anyof the above-discussed functionality with respect to FIG. 9 . In anembodiment, the processing of block 1206 includes generating a pointcloud from the received return RADAR signals; comparing RADAR points inthe point cloud to a location of a dock wall; and, identifying the atleast one obstacle based on ones of the RADAR points corresponding to alocation in the point cloud that is behind a location of the dock wallin the point cloud as shown and discussed above with respect to FIGS. 8and 11A/B.

Block 1208 includes initiating a maneuver of the trailer when thereceived return RADAR signals indicate an obstacle is located behind thetrailer. In one example of operation of block 1208, controller 206implements the machine readable instructions implementing themaneuvering module 240 to control the tractor 104 to stop, changecourse, or otherwise maneuver based on location of the trailer withrespect to location of obstacles 281 defined in memory 210.

CROSS-REFERENCE TO RELATED APPLICATIONS

Features described herein may be combined in many ways as understood bythose of ordinary skill in the art. The following is a list of potentialcombination of elements but is not limiting. Other combination offeatures may be made without departing from the scope hereof.

(A1) In an embodiment of a first aspect, a system for backing a trailercomprises: a radio detection and ranging (RADAR) device adapted to mounton a tractor with a field-of-view (FOV) rearward of the tractor suchthat, when the tractor is coupled to the trailer, the FOV is under thetrailer.

(A2) In the embodiment designated as (A1) of the first aspect, thesystem further includes a controller coupled to the RADAR device andoperable to: control the RADAR device to transmit a plurality oftransmitted signals within the FOV.

(A3) In either embodiment designated as (A1) or (A2) of the firstaspect, the controller is further operable to: receive, from the RADARdevice, at least one return signal being at least one reflection of atleast one of the plurality of transmitted signals and corresponding toan obstacle behind the trailer, the return signal defining a perceivedlocation of the obstacle.

(A4) In any embodiment designated as (A3) of the first aspect, thecontroller is further operable to: determine a correct location of theobstacle based on the perceived location and a number of reflectionsmade by the return signal.

(A5) In any embodiment designated as (A3) through (A4) of the firstaspect, the controller is further operable to: to determine the numberof reflections based on a position of a dock wall and a trailer facerelative to the RADAR device and the perceived location.

(A6) In any embodiment designated as (A5) of the first aspect, thecontroller is further operable to: the controller further operable todetermine a location of the dock wall relative to the RADAR device basedon a defined geographic location of the dock wall and a reportedgeographic location and orientation of the tractor.

(A7) In any embodiment designated as (A5) through (A6) of the firstaspect, the controller is further operable to determine a location ofthe dock wall relative to the RADAR device based on received LIDAR datacaptured by LIDAR mounted to the tractor.

(A8) In any embodiment designated as (A5) through (A9) of the firstaspect, the return signal defining the perceived location within athree-dimensional space relative to the RADAR device.

(A9) In any embodiment designated as (A5) through (A8) of the firstaspect, the controller is further operable to determine a location ofthe dock wall relative to the RADAR device based on groupings of returnsignals.

(A10) In any embodiment designated as (A9) of the first aspect, thecontroller is further operable to correlate the groupings to a definedgeographic location of the dock wall.

(A11) In any embodiment designated as (A10) of the first aspect, thecontroller is further operable to determine the defined geographiclocation of the dock wall based on one or more of image data, LIDARdata, and ultrasonic data received from at least one external sensordistinct from the RADAR device.

(A12) In any embodiment designated as (A1) through (A11) of the firstaspect, the controller is further operable to correlate a lineargrouping of return signals from the RADAR device to the dock wall.

(A13) In any embodiment designated as (A1) through (A11) of the firstaspect, the controller further operable to correlate a linear groupingof return signals from the RADAR device to the trailer face of thetrailer.

(A14) In any embodiment designated as (A1) through (A14) of the firstaspect, the controller further operable to correlate the linear groupingof return signals to a location of a back end of the trailer defined bya trailer angle relative to the tractor and a current location andorientation of the tractor.

(A15) In any embodiment designated as (A1) through (A14) of the firstaspect, the controller further operable to correlate multiple returnsignals to the obstacle.

(B1) In an embodiment of a second aspect, a method for backing a trailerincludes: estimating a dock wall and a trailer face.

(B2) In the embodiment designated as (B1) of the second aspect, themethod further includes classifying radio detection and ranging (RADAR)return signals according to a number of reflections of a correspondingRADAR transmitted signal.

(B3) In either embodiment designated as (B1) or (B2) of the secondaspect, the method further includes updating classifications accordingto velocity property of the RADAR return signals.

(B4) In any embodiment designated as (B1) through (B3) of the secondaspect, the method further includes correcting position of the RADARreturn signals according to the classifications.

(B5) In any embodiment designated as (B1) through (B4) of the secondaspect, the method further includes flagging obstacles positioned behindthe trailer based upon the corrected position of the RADAR returnsignals.

(B6) In any embodiment designated as (B1) through (B5) of the secondaspect, the step of estimating the dock wall includes determining thelocation of the dock wall from a defined geographic location of the dockwall.

(B7) In any embodiment designated as (B1) through (B6) of the secondaspect, the step of classifying the RADAR return signals includesdetermining the number of reflections is zero when the perceivedlocation is positioned at or before the dock wall, the number ofreflections is one when the perceived location is positioned beyond thedock wall less than a distance between the dock wall and the trailerface, and the number of reflections is two when the perceived locationis positioned beyond the dock wall more than the distance between thedock wall and the trailer face.

(B8) In any embodiment designated as (B1) through (B7) of the secondaspect, the step of classifying the RADAR return signals comprisingdetermining the number of reflections is zero when a first velocitydefined by the RADAR return signals is equal to a second velocity of thetractor, the number of reflections is one when the first velocitydefined by the RADAR return signals is greater than the second velocityof the tractor and less than twice the second velocity of the tractor,and the number of reflections is two when the first velocity defined bythe RADAR return signals is greater than twice the second velocity ofthe tractor and less than thrice the second velocity of the tractor.

(B9) In any embodiment designated as (B1) through (B8) of the secondaspect, the method is implemented on any embodiment designated as (A1)through (A15).

(C1) In an embodiment of a third aspect, a method for maneuvering atrailer, includes: transmitting a radio detection and ranging (RADAR)transmitted signal beneath the trailer.

(C2) In the embodiment designated as (C1) of the third aspect, themethod further includes receiving return RADAR signals based on thetransmitted signal.

(C3) In either embodiment designated as (C1) or (C2) of the thirdaspect, the method further includes processing the return RADAR signalsto identify at least one obstacle behind the trailer.

(C4) In any embodiment designated as (C1) through (C3) of the thirdaspect, the method further includes initiating a maneuver of the trailerwhen the return RADAR signals indicate an obstacle is located behind thetrailer.

(C5) In any embodiment designated as (C1) through (C4) of the thirdaspect, the processing the return RADAR signals includes identifying anumber of reflections of one or more of the return RADAR signals.

(C6) In any embodiment designated as (C1) through (C5) of the thirdaspect, the processing includes: generating a point cloud from thereturn RADAR signals.

(C7) In any embodiment designated as (C6) of the third aspect, theprocessing includes: comparing RADAR points in the point cloud to alocation of a dock wall.

(C8) In any embodiment designated as (C6) through (C7) of the thirdaspect, the processing includes: identifying the at least one obstaclebased on ones of the RADAR points corresponding to a location in thepoint cloud that is behind the location of the dock wall in the pointcloud.

(C9) In any embodiment designated as (C1) through (C8) of the thirdaspect, the processing includes: identifying the dock wall in the pointcloud based on a linear grouping of the RADAR points in the point cloud.

(C10) In any embodiment designated as (C1) through (C9) of the thirdaspect, the method further comprising receiving position of the dockwall as defined using a LIDAR or defined in a yard-map.

(C11) In any embodiment designated as (C10) of the third aspect, theprocessing includes correlating the position of the dock wall to thepoint cloud.

(C12) In any embodiment designated as (C1) through (C11) of the thirdaspect, the initiating a maneuver includes autonomously controlling anautonomous yard vehicle coupled to the trailer.

(C13) In any embodiment designated as (C1) through (C12) of the secondaspect, the method is implemented on any embodiment designated as (A1)through (A15).

Changes may be made in the above methods and systems without departingfrom the scope hereof. It should thus be noted that the matter containedin the above description or shown in the accompanying drawings should beinterpreted as illustrative and not in a limiting sense. The followingclaims are intended to cover all generic and specific features describedherein, as well as all statements of the scope of the present method andsystem, which, as a matter of language, might be said to falltherebetween.

What is claimed is:
 1. A system for backing a trailer, comprising: aradio detection and ranging (RADAR) device adapted to mount on a tractorwith a field-of-view (FOV) rearward of the tractor such that, when thetractor is coupled to the trailer, the FOV is under the trailer; and acontroller coupled to the RADAR device and operable to: control theRADAR device to transmit a plurality of transmitted signals within theFOV, receive, from the RADAR device, at least one return signal being atleast one reflection of at least one of the plurality of transmittedsignals and corresponding to an obstacle behind the trailer, the returnsignal defining a perceived location of the obstacle, and determine acorrect location of the obstacle based on the perceived location and anumber of reflections made by the return signal.
 2. The system of claim1, the controller further operable to determine the number ofreflections based on a position of a dock wall and a trailer facerelative to the RADAR device and the perceived location.
 3. The systemof claim 2, the controller further operable to determine a location ofthe dock wall relative to the RADAR device based on a defined geographiclocation of the dock wall and a reported geographic location andorientation of the tractor.
 4. The system of claim 2, the controllerfurther operable to determine a location of the dock wall relative tothe RADAR device based on received LIDAR data captured by LIDAR mountedto the tractor.
 5. The system of claim 2, the return signal defining theperceived location within a three-dimensional space relative to theRADAR device.
 6. The system of claim 2, the controller further operableto determine a location of the dock wall relative to the RADAR devicebased on groupings of return signals.
 7. The system of claim 6, thecontroller further operable to correlate the groupings to a definedgeographic location of the dock wall.
 8. The system of claim 7, thecontroller further operable to determine the defined geographic locationof the dock wall based on one or more of image data, LIDAR data, andultrasonic data received from at least one external sensor distinct fromthe RADAR device.
 9. The system of claim 6, the controller furtheroperable to correlate a linear grouping of return signals from the RADARdevice to the dock wall.
 10. The system of claim 6, the controllerfurther operable to correlate a linear grouping of return signals fromthe RADAR device to the trailer face of the trailer.
 11. The system ofclaim 10, the controller further operable to correlate the lineargrouping of return signals to a location of a back end of the trailerdefined by a trailer angle relative to the tractor and a currentlocation and orientation of the tractor.
 12. The system of claim 6, thecontroller further operable to correlate multiple return signals to theobstacle.
 13. A method for backing a trailer, comprising: estimating adock wall and a trailer face; classifying radio detection and ranging(RADAR) return signals according to a number of reflections of acorresponding RADAR transmitted signal; updating classificationsaccording to velocity property of the RADAR return signals; correctingposition of the RADAR return signals according to the classifications;and flagging obstacles positioned behind the trailer based upon thecorrected position of the RADAR return signals.
 14. The method of claim13, the step of estimating the dock wall comprising determining thelocation of the dock wall from a defined geographic location of the dockwall.
 15. The method of claim 13, the step of classifying the RADARreturn signals comprising determining the number of reflections is zerowhen the perceived location is positioned at or before the dock wall,the number of reflections is one when the perceived location ispositioned beyond the dock wall less than a distance between the dockwall and the trailer face, and the number of reflections is two when theperceived location is positioned beyond the dock wall more than thedistance between the dock wall and the trailer face.
 16. The method ofclaim 13, the step of classifying the RADAR return signals comprisingdetermining the number of reflections is zero when a first velocitydefined by the RADAR return signals is equal to a second velocity of thetractor, the number of reflections is one when the first velocitydefined by the RADAR return signals is greater than the second velocityof the tractor and less than twice the second velocity of the tractor,and the number of reflections is two when the first velocity defined bythe RADAR return signals is greater than twice the second velocity ofthe tractor and less than thrice the second velocity of the tractor. 17.A method for maneuvering a trailer, comprising: transmitting a radiodetection and ranging (RADAR) transmitted signal beneath the trailer;receiving return RADAR signals based on the transmitted signal;processing the return RADAR signals to identify at least one obstaclebehind the trailer; and initiating a maneuver of the trailer when thereturn RADAR signals indicate an obstacle is located behind the trailer.18. The method of claim 17, the processing the return RADAR signalsincluding identifying a number of reflections of one or more of thereturn RADAR signals.
 19. The method of claim 17, the processingincluding: generating a point cloud from the return RADAR signals;comparing RADAR points in the point cloud to a location of a dock wall;and identifying the at least one obstacle based on ones of the RADARpoints corresponding to a location in the point cloud that is behind thelocation of the dock wall in the point cloud.
 20. The method of claim19, the processing further including identifying the dock wall in thepoint cloud based on a linear grouping of the RADAR points in the pointcloud.
 21. The method of claim 19, further comprising receiving positionof the dock wall as defined using a LIDAR or defined in a yard-map; theprocessing further comprising correlating the position of the dock wallto the point cloud.
 22. The method of claim 17, the initiating amaneuver including autonomously controlling an autonomous yard vehiclecoupled to the trailer.